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Flashcards in Endocrine System Test Deck (27):

what does the endocrine system consist of ?

endocrine glands
secreting cells in organs



diffuse from interstitial fluid to bloodstream & eventually to other cells called TARGET CELLS


Characteristics of endocrine system
what do hormones affect? what do they contain? receptors?

hormones affect target cells that respond to a specific hormone
-contain SPECIFIC RECEPTORS (proteins or glyoproteins)
-'site specific' (only accept 1 type of hormone)


Hormone types (2)

non-steroid (water-soluble)
steroid (lipid-soluble)


non-steroid includes what?

amines, peptides, proteins, glycoproteins


steroid includes?

steroid hormones, thyroid hormones, nitric oxide (NO)


lipid-soluble (steroid) hormones

insoluble in water- but soluble in other lipids (EASY to enter cell membrane)
all derived from cholesterol
takes longer to act, but generally effects last longer than non-steroid hormones
-EX) puberty takes longer to act but lasts longer


action of steroid hormones

hormones transported in blood by transport proteins
diffuse through cell membrane (lipid bilayer) & bind to receptors within target cells


water soluble (non-steroid) hormones

composed of amine acids
cant diffuse through lipid-bilayer
bind to receptors on target cell surface
act faster, but effects are more short-lived than steroid hormones
EX) scared, heart rate increase (fight or flight)


Steroid hormone action (how steroid hormones work)

1) lipid soluble steroid hormone enters the target cell directly through cell membrane and binds to specific receptor (activation).
2) Activated hormone-receptor complex binds to specific genes of target cell's DNA & causes these genes to be expressed.
3) mRNA from hormone-activated genes leaves nucleus & starts to make new proteins
4) new proteins alter cell's activity in some specific way


Non-steroid hormone action (how non-steroid hormones work)

1) Water-soluble non-steroid hormone = first chemical message. Binds to specific receptor ON cell membrane of target cell (activation)
2) Hormone receptor complex stimulates formation of a SECOND messenger inside cell (cAMP). cAMP made from ATP by enzyme adenylate cyclase.
3) cAMP activates protein kinase enzymes -> activate other proteins by phosphorylation (adding phosphate)
4) many phosphorylated proteins alter cell's activity to elicit physiological responses
5) cAMP only lasts for short time before degraded


non-steroid vs steroid hormones

steroid: enters cell membrane, insoluble in water (transport proteins, receptors in target cell)
derived from cholesterol
long to act, effects last long
non-steroid: can't diffuse through lipid-bilayer (already has proteins, receptor on membrane)
composed of amino acids
act fast, short effects


Affect of aging on what 5 glands?



affects of aging on thymus gland

thymus gland shrinks significantly causing decreased immune cell production & decreased resistance to disease


affects of aging on pituitary gland

hGH secretion decreases, leading to muscle atrophy and weakness


affects of aging on kidneys

calcitriol secretion diminishes


affects of aging on pineal gland

secretion of melatonin is reduced w/ age, disrupts normal sleep-wake cycles


affects of aging on pancreas

insulin secretion and sensitivity of target tissue diminishes, affects changes in blood glucose ; increases = faster & return to normal glucose levels = more slowly


3 ways /methods hormones are controlled by the body

1. signals from NERVOUS SYSTEM
2. Chemical changes in BLOOD


Describe how hormones are controlled by the signals from the nervous system

nervous system -> endocrine gland -> target cells-> action


Describe how hormones are controlled by the chemical changes in the blood

blood -> endocrine gland -> target cells -> action


Describe how hormones are controlled by other hormones acting on each other?

hypothalamus -> ant. pituitary -> peripheral endocrine gland-> target cells -> action


how are hormonal secretions controlled in general?

controlled using negative feedback
1. Secretion triggered by internal/external stimulus
2. Rising hormone levels inhibit further hormone release in target organ


negative feedback of insulin

blood sugar level is high -> insulin is secreted, the change in blood glucose levels is detected, hypothalamus stops stimulating insulin production


negative feedback of glucagon

blood sugar level is low -> glucagon is secreted, the increase in blood glucose levels is detected, hypothalamus stops stimulating glucagon production


where is insulin and glucagon made? effect on body?

made in- pancreas
insulin-secreted by beta cells in pancreas, lowers blood glucose
glucagon- secreted by alpha cells in pancreas, raises blood glucose


explain how nervous & endocrine system work together?ex of hormone and effect when stimulated? how messages are sent?

-nervous system receives internal/external stimulus ie physical harm, body temp, etc
-stimulus is sent to brain for interpretation
-bc hypothalamus is link btwn nervous & endocrine systems, it stimulates the pituitary gland to produce certain hormones that are then sent to an endocrine gland w/ target cells
-EX) you're asleep & house catches on fire.
-change in body temp alerts nervous system
-stimulus sent to brain
-interpreted as "danger"
-hypothalamus stimulates pituitary gland
-pituitary secretes ACTH
-ACTH travels through blood stream & stimulates adrenal glands to release epinephrine & norepinephrine which allows increased focus and mobility to get out of the house as a flight or fight response